HTTP Status 402 - Payment Required

GET /api/premium-data HTTP/1.1
Host: api.example.com
Authorization: Bearer token123

HTTP/1.1 402 Payment Required
Content-Type: application/json

{
  "error": "quota_exceeded",
  "message": "Free tier limit reached. Upgrade to Pro for unlimited requests.",
  "upgrade_url": "https://api.example.com/pricing"
}

GET /api/features/advanced HTTP/1.1
Host: api.example.com
Authorization: Bearer token456

HTTP/1.1 402 Payment Required
Content-Type: application/json

{
  "error": "subscription_expired",
  "message": "Your subscription expired on 2025-09-30",
  "renew_url": "https://billing.example.com/renew",
  "grace_period_until": "2025-10-15"
}

POST /api/reports/custom HTTP/1.1
Host: api.example.com

HTTP/1.1 402 Payment Required
Content-Type: application/json

{
  "error": "premium_feature",
  "message": "Custom reports require Business tier subscription",
  "current_plan": "Starter",
  "required_plan": "Business",
  "pricing": "https://api.example.com/pricing#business"
}